leetcode-12-path sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,
5
/
4 8
/ /
11 13 4
/
7 2 1
return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

给定一棵二叉树，判断是否有从根到叶子节点的路径和等于给定值。

一个简单的递归调用函数即可。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool hasPathSum(TreeNode* root, int sum) {
        if(!root) return false;
        sum-=root->val;
        return hasPathSum(root->left,sum)||hasPathSum(root->right,sum)||(!root->left&&!root->right&&sum==0);
    }
};